B. Protein Blotting

A general protocol for sample preparation.

Lyse cells by adding 1X SDS sample buffer (100 µl per well of 6-well plate or 500 µl for a 10 cm diameter plate). Immediately scrape the cells off the plate and transfer the extract to a microcentrifuge tube. Keep on ice.

Western Blot Reprobing Protocol

Reprobing of an existing membrane is a convenient means to immunoblot for multiple proteins independently when only a limited amount of sample is available. It should be noted that for the best possible results a fresh blot is always recommended. Reprobing can be a valuable method but with each reprobing of a blot there is potential for increased background signal. Additionally, it is recommended that you verify the removal of the first antibody complex prior to reprobing so that signal attributed to binding of the new antibody is not leftover signal from the first immunoblotting experiment. This can be done by re-exposing the blot to ECL reagents and making sure there is no signal prior to adding the next primary antibody.

(Optional) To assure that the original signal is removed, wash membrane twice for 5 min each with 10 ml of TBST. Incubate membrane with LumiGLO® with gentle agitation for 1 min at room temperature. Drain membrane of excess developing solution. Do not let dry. Wrap in plastic wrap and expose to x-ray film.

Wash membrane again four times for 5 min each in TBST.

The membrane is now ready to reuse. Start detection at the "Membrane Blocking and Antibody Incubations" step in the Western Immunoblotting Protocol.

Species Reactivity:

The Grb-associated binder (Gab) family is a family of adaptor proteins recruited by a wide variety of receptor tyrosine kinases (RTKs) such as EGFR, HGFR, insulin receptor, cytokine receptor and B cell antigen receptors. Upon stimulation of RTKs by their cognate ligand, Gab is recruited to the plasma membrane where it is phosphorylated and functions as a scaffold (1-4). Multiple tyrosine phosphorylation sites of Gab1 protein have been identified (5). Phosphorylation of Tyr472 regulates its binding to p85 PI3 kinase (6,7). Phosphorylation of Gab1 at Tyr307, Tyr373 and Tyr407 modulates its association to PLCγ (8). Phosphorylation of Tyr627 and Tyr659 is required for Gab1 binding to and activation of the protein tyrosine phosphatase SHP2 (6,9).

Gab2, a recently identified docking protein of Gab family, contains a pleckstrin homology domain and potential binding sites for SH2 and SH3 domain-containing proteins. Gab2 has been shown to support growth, differentiation and function in a number of hematopoietic cells (10).